Fuji_Abound wrote:
Perhaps that depends, “proving” the props are going to feather is a potential life saver in a twin.
In my book, since I fly twins, the “feather” check is performed so quickly that the propeller blades do not actually move into the feather position. It’s purpose is to check that the prop levers can be moved all the way past the catch into the end position. Actually feathering the prop can stall the engine (like shifting the car into high gear at low speed) and the starter motor will have a hard time getting the engine going again with the blades in that position. (I know because a student did it once and I was not quick enough…). This is what the manual of the Seminole we train on has to say regarding the “feather check” – Piper calls it “ground check”: Set the throttles to an engine speed of 1500RPM. Retard the propeller controls aft to check feathering; however, do not allow a drop of more than 500 RPM.
But anyway, the prop governor does not care the least where the wind comes from when one performs the engine runup. And regarding possible overheating: As we train IFR from an international airport using slowish aircraft, they always need a large gap in order to “shoot” us from the runway. This often means long waits at the holding position (my record being 55 minutes) with the engine at low RPM and the wind coming at any speed from any direction. So far I have not seen an engine overheat on the ground.
RobertL18C wrote:
It may fall in the same category to cycling the propeller several times, which is not ideal for the crankshaft
Why would this not be ideal for the crankshaft?
You cycle the prop at really low power, you do not need to do it brutally like some instructors have shown me who used to yank the blue lever all the way back and then forward again.
If cycling the prop during run-up is bad for the crankshaft, then I do not dare to think about what it does to it when you pull back from 2600 RPM to 2300-2500 RPM at 70% BHP.
I try to point into the wind if it is significant for the particular aircraft flown. It will be smoother and the flight controls will not feel “restless” and stir around. When I fly taildraggers I certainly pay more attention to this than if I it is nosewheeler. To me it is the same as why you use ailerons into the wind during taxiing, it is not critical but I get a sense that the flight controls feels better when doing it.
I think on any aircraft with a VP prop isnt “excercising the prop.” about getting some warm oil around the bearings? In a twin it is pretty obvious the feather locks are engaging, and isnt it usual to test the locks once at relatively low rpm – typically around 1600? Any twin used for training will regularly “experience” the prop being feathered from high rpm in flight so one would rather hope the crank is up to it as long as the procedure is carried out sensibly.
Fuji_Abound wrote:
I think on any aircraft with a VP prop isnt “excercising the prop.” about getting some warm oil around the bearings?
Yes, and more importantly into the governor itself. It is a large piston operated with normal engine oil at engine oil pressure (i.e. at fairly low pressure). Therefore it needs to be large and requires a considerable volume of oil. After a cold night, this oil is very viscuous and initially the propeller does not like to move at all – until all the cold oil is replaced with warm oil from the engine. On a warm day or shortly after the last flight the governor will work smoothly at the first attempt, so moving the lever once is enough. On a cold day, three, five, ten or even more times may be required…
Fuji_Abound wrote:
Any twin used for training will regularly “experience” the prop being feathered from high rpm
Around here, actually feathering an engine in flight has been verboten since decades so I guess it is not done very often. No idea if they do it at the 50 and 100 hour checks.
Addition: This may sound slightly heretic to some, but still: I think that the importance of all those checks is vastly overestimated. In my experience, engines and airplane systems in general do not fail on the ground between flights. If you landed with a fully functional aircraft, then chances are 99% that it will still be fully functional before the next takeoff. The stuff always fails in flight and usually at the worst possible time (i.e. de-ice boots which had worked perfectly well during those pre-flight checks but whose valves were frozen shut when we would have needed them…). If it were not for the evidence on the cockpit voice recorder I would skip those checks altogether.
what_next wrote:
On a cold day, three, five, ten or even more times may be required…
Coming back to my favourite article series, this is what John Deakin has to say about it:
How many times should you cycle the prop? If the RPM drops smoothly and properly, once is enough. The fresh oil will probably cause the piston to move a good deal and when it comes back to the low pitch stops, most of the “old” oil will be pushed out. If you really want to feel good, do it twice, to get even more of that “old” oil out of there. Three times is gross overkill, in my opinion, but a lot of people do three times, or more. In reality, there are tiny bleed holes that allow a constant flow of warm oil to both sides of the prop piston, so even if you take off with cold oil in there, it will quickly be replaced with nice slippery warm stuff. On some of the big old props on the radials, in extreme Arctic conditions, the oil would congeal faster than the bleed ports could replace it, but I doubt you’ll find any modern props with this problem. I should note for completeness that many of the props on the big radials might require many more cycles to achieve a smooth RPM drop when cold. In freezing temperatures, it may take up to ten cycles. There’s a lot more to the mechanism, and a lot more oil involved.
Are you flying big radial engines? 
In my humble opinion, letting the oil heat up and then doing one cycle (or just waiting a bit) should be more effective than to do ten cycles with the same, cold oil.
what_next wrote:
Around here, actually feathering an engine in flight has been verboten since decades so I guess it is not done very often. No idea if they do it at the 50 and 100 hour checks.
I am not sure which countries now require an engine shut down in flight at the initial skills test, and which countries require simulated failures?
I am not sure which of the main ground checks on most GA SEPs or MEPS are truly redundant or at least dont have some merit.
Mags – I have had more than a few occasions when the mag check has revealed a problem,
Feathering an excercise – I have never had a prop. fail to feather but as discussed it makes sense to get some warm oil into the system,
Flight controls – well missed rigging and missed ground rash does occur and may well be caught,
Doors etc – we have all departed with an unhinged door, havent we?,
Autopilot – we have all had an autopilot go u/s and it might just fail or already have failed on the ground so useful to catch it at that stage,
Trim – always a pain to find the trim hasnt been checked and set,
Tank change – I have actually never had a problem changing tanks but I am sure it has happened to some?
I still find whatever I fly I give the seat a good shove back, it often isnt on the checklist but if they are going to move isnt it always just after you rotate. :-)
Perhaps that depends, “proving” the props are going to feather is a potential life saver in a twin.
The feather mechanism, and check, are independent of cycling the propeller governor.
Rwy20 wrote:
In my humble opinion, letting the oil heat up and then doing one cycle (or just waiting a bit) should be more effective than to do ten cycles with the same, cold oil.
Probably yes. But one can easily feel it. Slowly move the prop lever and if the RPM follows the lever smoothly, then everything is OK. If the lever is stiff to more and/or there is some lag between lever position and RPM indication, move it again…
RobertL18C wrote:
The feather mechanism, and check, are independent of cycling the propeller governor.
Yes, I wasnt intending to suggest otherwise.
